81749205988 has 6 divisors (see below), whose sum is σ = 143061110486. Its totient is φ = 40874602992.

The previous prime is 81749205977. The next prime is 81749206003. The reversal of 81749205988 is 88950294718.

It can be written as a sum of positive squares in only one way, i.e., 48198689764 + 33550516224 = 219542^2 + 183168^2 .

It is a super-2 number, since 2×81749205988² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10218650745 + ... + 10218650752.

Almost surely, 2^81749205988 is an apocalyptic number.

It is an amenable number.

81749205988 is a deficient number, since it is larger than the sum of its proper divisors (61311904498).

81749205988 is a wasteful number, since it uses less digits than its factorization.

81749205988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20437301501 (or 20437301499 counting only the distinct ones).

The product of its (nonzero) digits is 11612160, while the sum is 61.

The spelling of 81749205988 in words is "eighty-one billion, seven hundred forty-nine million, two hundred five thousand, nine hundred eighty-eight".